Load and Resistance Factor Design Rules

sign philosophies for designing structures are cur 

rently in use.  The LRFD philosophy utilizes proba 

The University of New Orleans, College of Engi 

bilistic methods as opposed to pure static and dy 

neering  teamed  with  the  University  of  Maryland,

namic formulas used in the ASD philosophy.

College Park to develop new design rules utilizing

Advantages of the LRFD philosophy include a more

probabilistic  methods  to  reduce  weight  in  future

rational  approach  for  new  designs  and  configura 

commercial and naval vessel structures.

tions; consistency in reliability with the potential of

a more economical use of materials; building codes

The University of New Orleans, College of Engi 

can be calibrated by allowing for future changes as a

neering (UNO COE) saw a need for weight reduc 

result of gained information in predicted models, and

tion in today s shipbuilding market.  The U.S. Navy

material and load characterization.

is  now  requiring  the  use  of  light  gage  plate  in

nonstructural  and  structural  bulkheads  on  their

Production

LPD 17 and DDG 21 next generation warfighters.

On going committee studies were considered by the

team in the development of these new procedures

Advanced Composites Manufacturing

for the design of ship structures.  Initially, the Load

Technology

and Resistance Factor Design (LRFD) criteria is en 

visioned to be used in parallel with currently used

The University of New Orleans, College of En 

procedures.  The applications and limitations of this

gineering  participates  in  the  development  of  a

procedure are currently limited to the design of  fine

highly  capable  fiber  composite  system  and  con 

bow, bow with flare, or flat bottomed vessels and con 

tributes to a collaborative manufacturing environ 

ventional displacement type monohull surface ves 

ment  that  provides  considerable  economic  and

sels made of metallic materials, and with a length

educational opportunities.

between perpendiculars of 300 feet to1000 feet.

The old process to design vessels utilized Navy or

The University of New Orleans, College of Engi 

the American Bureau of Shipping rules.  New de 

neering (UNO COE), in partnership with the state

signs do not have historical information to use as a

of Louisiana, the National Aeronautics and Space

basis.  The team s objective in the first year was to

Administration (NASA), and Lockheed Martin Cor 

develop  LRFD  criteria  for  hull  girder  bending  of

poration at the Michoud Assembly Facility in New

surface  ship  structures  for  both  commercial  and

Orleans, is directly involved in the provision of re 

naval vessels.  In the second year, the team devel 

search, development, and education for manufac 

oped LRFD criteria for unstiffened panels of sur 

turing the next generation launch vehicle systems.

face  ship  structures,  and  in  the  third  year  of  the

State funding and NASA facilities have been com 

project,  it  developed  LRFD  criteria  for  fatigue  of

bined to provide UNO COE with an opportunity

surface ship structures.

to participate directly to effect an intelligent col 

The development of this new method for the struc 

laborative  manufacturing  environment,

tural design of conventional displacement type sur 

strengthen national competitiveness in aerospace/

face monohull ships is based on a structural reliabil 

commercial  markets,  develop  and  manufacture

ity theory in an LRFD format.  The LRFD rules can

composite materials, and expand regional economic

be used for early design of ship structures to check

development  and  advanced  manufacturing  tech 

adequacy in the detailed design stage.  For marine

nology education opportunities.

applications, LRFD development is based on special

Operating under the auspices of the National Cen 

and extreme analysis of wave loads with a combina 

ter  for  Advanced  Manufacturing  (NCAM),  UNO

tion of partially correlated loads.  Nominal strength

COE established significant cooperation with fed 

and load values, along with achieving target reliabil 

eral agencies, universities, the state, and industry.

ity  levels,  are  also  considered. The  LRFD  method

NCAM currently possesses and operates a highly

builds on conventional marine and structural codes.

capable fiber composites installation, and is in the

The design philosophy must provide for ship struc 

process of developing and obtaining a state of the 

tural designs that have adequate safety and allow

art system to advance this manufacturing technol 

for the proper functioning of each component.  The

ogy.  With the capability for seven axes and 24 tow

Allowable Stress Design (ASD) and the LRFD de 

fiber placements, the current composite fabrication

5